In an audio output interface mounted in a vehicle or the like, when plural pieces of audio information become output candidates at the same time, the audio outputs are arbitrated to restrict an output target. For example, in the prior art disclosed in PTL 1, the audio outputs are arbitrated in the following manner.
An arbitration table is created, and the arbitration table is implemented in software of a navigation system in advance. The arbitration table defines the priorities of the audio outputs to be arbitrated. When plural pieces of the audio information to be output in the navigation system are present at the same time, the audio information higher in order is preferentially output according to priorities based on the arbitration table.
The above prior art suffers from the following problems. The audio information has temporal characteristics that require a fixed period of time since the output starts until significant contents are transferred. For that reason, when the output of the audio information is interrupted on the way, necessary information may not be transmitted to a user. In the arbitration table in the prior art, the temporal characteristics of the audio information are not taken into consideration.
For example, in a situation where a request for outputting later audio information higher in priority is made while earlier audio information is being output, the output of the earlier audio information may be interrupted to output the later audio information by interruption as a result of the output arbitration based on the arbitration table. It is assumed to define “When an output A and an output B come together, the output B has priority, and the output A is implemented after the output B has ended.” in the arbitration table. According to that definition, when an event of the latter output B occurs just before the earlier output A ends, even if the output A leaves only slight wording of an end of a sentence, the output A is interrupted, and the remaining of the output A is output after the output B has been completed. In that case, the start of the output B has only to be slightly delayed, but the prior art does not take the temporal characteristics of the audio information into consideration, as a result of which wording meaningless to the user would be output later.
Alternatively, when the later audio information is interrupted before the significant contents in the earlier audio information are completely transmitted, the later audio information may sound like unnatural audio information not meaningful to the user. When the plural audio outputs are arbitrated without taking the temporal characteristics of the audio information into consideration, the interrupt of the audio outputs is likely to occur at unnatural timing for the user.